1. Field of the Invention
The present invention relates generally to a hand tool, and more particularly, to a universal joint for a hand tool.
2. Description of the Related Art
Most of the conventional universal joints each are composed of two components. For example, U.S. Patent Laid-open No. 2009/0288523 disclosed a universal joint composed of a rod, a polyhedral sphere, and a socket having a polyhedral cavity for receiving and engaging the polyhedral sphere. The cavity includes a groove formed at an opening thereof for a restraining element to fit therein in such a way that the polyhedral sphere can be restrained within the cavity. When this universal joint is used, the polyhedral engagement between the polyhedral cavity and the polyhedral sphere can prevent the polyhedral sphere from axial rotation with respect to the cavity, and the polyhedral sphere can pivot within a predetermined range for a predetermined angle. However, when the rod is operated to pivot, the surfaces of the polyhedral sphere are slidably moved with respect to the internal surfaces of the polyhedral cavity while keeping in contact with the internal surfaces of the cavity, such that the operation is not smooth.
In addition, U.S. Pat. No. 6,869,366 disclosed that a driven socket 14 includes a plurality of channels 32 formed at a bottom end thereof, and a driver 12 located below the driven socket 14 and having a plurality of inwardly extending protrusions 52 corresponding to the channels 32. In this way, the driver 12 can be forced to pivot universally with respect to the driven socket 14 without axial rotation. Besides, the proprietor of this patent has another U.S. Pat. No. 6,152,826, which has the similar structure and the same effect.
In the above two patents, the channels 32 are used for engaging the inwardly extending protrusions 52 for the universal jointure. However, in the actual operation, when the driver is pivoted with respect to the driven socket, the channels 32 can be moved limitedly within the inwardly extending protrusions 52. As can be seen from this, the inwardly extending protrusions 52 each must have a predetermined length for the stroke of the channels 32. In other words, the driven socket must have sufficient length to receive the inwardly extending protrusions. However, such structure makes the whole universal joint larger to increase the production cost.